1. Field of the Invention
This invention relates to apparatus for discriminating between acceptable and unacceptable coins. More particularly, the invention is used to test coins fed to vending machines of various types, such as coin-operated laundries, electronic games and dispensing machines for food and the like. The invention represents an improvement over earlier U.S. Pat. Nos. 3,978,962 and 4,089,400.
2. Prior Art
The use of coin-operated and controlled devices is widespread, and includes such diverse mechanisms as electronic games, coin-operated laundries, pay telephones, toll stations, food vending machines and the like. Since such devices are typically left unattended, they are particularly susceptible to vandalism and abuse. Operators of such machines lose large sums of revenue due to fraudulent use of bogus coins, tokens and the technique of "stringing", which entails the use of a string attached to a coin of proper value which is inserted into the apparatus by the user and then withdrawn after all of the tests are passed, thereby obtaining a free vend.
Various efforts have been made in the prior art to defeat such fraudulent use of the vending machines, including means for detecting and measuring selected parameters of a coin supplied to the apparatus. Examples of some such devices are disclosed in the aforementioned U.S. Pat. Nos. 3,978,962 and 4,089,400 and the patents cited therein.
Most of these devices are relatively complex and expensive, and are, themselves, subject to abuse. For instance, the majority of coin testing devices presently in use rely upon mechanical testing means for testing the physical size and metal content of the coins. Experience has shown that these devices can be defeated or rendered inoperable by introducing foreign material into the mechanism or by applying a sharp blow to it. Many of the devices can be "fooled" by dropping a coin of proper value into the machine, but then withdrawing the coin by means of a string attached to it after all of the tests have been passed.